Gas supply plant for compressed gas-insulated switchgear

ABSTRACT

A switchgear plant includes a plurality of gas-pressurized switchgear sections each of which includes a high pressure chamber containing a contact switching section, a low pressure chamber connected to the high pressure chamber by a blast valve which opens upon contact separation to effect a flow of gas from the high pressure to the low pressure chamber, and gaspressurized insulating bulkhead chambers located adjacent the high and low pressure chambers and which include isolating switches connected in series with the switching contacts. Branch gas return pipes including pressure differential responsive oneway valves therein lead from the low pressure chambers to a common return pipe connected to the intake side of a compressor, and the outlet side of the compressor is connected to a common high pressure gas supply pipe from which branch pipes containing pressure differential responsive non-return valves lead to the high pressure chambers. Pressure monitors associated with the low pressure chambers control operation of the compressor and other pressure monitors associated with the high pressure chambers actuate a central control valve that connects the compressor outlet as well as a high pressure gas reservoir with the common high pressure gas supply pipe. A pressurized gas supply pipe common to all of the insulating bulkhead chambers is connected to a reserve gas cylinder through a control valve, branch pipes lead off from this supply pipe at each switchgear section to the insulating bulkhead chambers through pressure differential responsive non-return valves and pressure monitors associated with the insulating bulkhead chambers serve to actuate the valve controlling gas flow from the reserve gas cylinder to replenish gas which may have been lost from the insulating bulkhead chambers through leakage.

United. States Patent 1191 Wagner et al.

[451 Nov. 19, 1974 GAS SUPPLY PLANT FOR COMPRESSED GAS-INSULATED SWITCHGEAR [75] Inventors: Karl Heinz Wagner,

Mannheim-Kafertal; Reiner Muellerpoths; Rudolf Hammel, both of Mannhein, all of Germany [73] Assignee Brown, Boveri & Company Limited, Baden, Switzerland [22] Filed: May 14, 1973 [21] Appl. No.: 360,068

[30] Foreign Application Priority Data May 16, 1972 Germany 2223753 [52] U.S. Cl 200/148 R, 200/148 E [51] Int. Cl. H01h 33/80 [58] Field of Search 200/148 E, 148 B, 148 R [56] References Cited UNITED STATES PATENTS 2,955,182 10/1960 Caswell et al. 200/148 E 3,566,062 2/1971 Meier et al 200/148 E 3,614,355 10/1971 Boersma 200/148 E 3,637,965 l/1972 Schmitz.... 200/148 E 8/1972 Schmitz 200/148 E Primary ExaminerRobert S. Macon Attorney, Agent, or Firm-Pierce, Scheffler & Parker [57] ABSTRACT A switchgear plant includes a plurality of gaspressurized switchgear sections each of which includes a high pressure chamber containing a contact switching section, a low pressure chamber connected to the high pressure chamber by a blast valve which opens upon contact separation to effect a flow of gas from the high pressure to the low pressure chamber, and gas-pressurized insulating bulkhead chambers located adjacent the high and low pressure chambers and which include isolating switches connectedin series with the switching contacts. Branch gas return pipes including pressure differential responsive one-way valves therein lead from the low pressure chambers to a common return pipe connected to the intake side of a compressor, and the outlet side of the compressor is connected to a common high pressure gas supply pipe from which branch pipes containing pressure differential responsive non-return valves lead to the high pressure chambers. Pressure monitors associated with the low pressure chambers control operation of the compressor and other pressure monitors associated with the high pressure chambers actuate a central control valve that connects the compressor outlet as well as a high pressure gas reservoir with the common high pressure gas supply pipe. A pressurized gas supply pipe common to all of the insulating bulkhead chambers is connected to a reserve gas cylinder through a control valve, branch pipes lead off from this supply pipe at each switchgear section to the insulating bulkhead chambers through pressure differential responsive non-return valves and pressure monitors associated with the insulating bulkhead chambers serve to actuate the valve controlling gas flow from the reserve gas cylinder to replenish gas which may have been lost from the insulating bulkhead chambers through leakage.

5 Claims, 1 Drawing Figure GAS SUPPLY PLANT FOR COMPRESSED GAS-INSULATED SWITCHGEAR This invention relates to an improvement in a gas supply plant with closed gas circulation for switchgear insulated by compressed gas, particularly SP the switchgear comprising a high pressure and a low pressure part, wherein the high pressure part is connected to the low pressure part by way of switching sections provided with blast valves and the gas is returned from the low pressure part to the high pressure part by means of one of more compressors, and wherein the gas pressures in the high pressure and low pressure parts, and in the individual insulating bulkhead compartments of the installation, is monitored and controlled by respectively associated valves of the solenoid operated type. A compressed gas-insulated switchgear with a gas supply system arranged in this manner is dis closed, for example, in German Open Print No. 1,916,560.

A particular problem in switchgear insulated by compressed gas (particularly SP and having two or more pressure switches arises in the provision of compressed gas for arc extinction, the suppression of the mixing of soiled extinguishing gas with the insulating gas, and the make-up of leakage losses in the individual bulkhead compartments of the switchgear. In known switchgear structures one control cabinet is provided for each three-pole air-blast circuit-breaker group, from which point all the switchgear of a feeder can be controlled and monitored.

The compressed air required for the circuit-breakers of the installation is here produced by means of compressors. The compressed air produced in this manner is stored in reservoirs. After reduction to an intermediate pressure, the compressed air is fed through a distributor plant to each control cabinet. In this known arrangement the reduction to operating pressure is effected by means of a refilling valve which is in the form of a solenoid valve installed in the control cabinet and which effects the automatic refilling of a circuitbreaker of the circuit-breaker group. The operation of each individual circuit-breaker group, or of each individual bulkhead chamber, by its own solenoid valve provided for the purpose nevertheless entails considerable expense.

The present invention seeks to provide a selfsufficient gas supply plant of the type discussed which,

by means of simpler components, complies with the same conditions as known constructions using expensive solenoid valves. In particular, the following should be achieved:

a. controlled replenishment of compressed gas only for those bulkhead compartments in which the gas pressure falls below the required level;

b. controlled exhaustion of the soiled extinction gas from the low pressure chamber which is at the highest gas pressure;

c. the overflow of soiled extinction gas into the insulating gas chambers should be reliably prevented, and

d. finally, the insulating gas should be prevented from flowing back from one bulkhead compartment into another or into the supply pipe in the event of a leak occurring in one of these elements.

According to the invention this problem is solved in a self-sufficient gas supply plant of the kind first described above by connecting each of the bulkhead chambers of the switchgear, in each of which practically identical gas pressures are to be maintained by replenishing or drawing off gas, to a common ring pipe which is connected either to a common compressed gas source for replacement of compressed gas or to a device (compressor) controlled in dependence on pressure for drawing off the gas, while for the purpose of replacing compressed gas, a central valve controlled in dependence on pressure is provided between the compressed gas source and the ring pipe, one-way valves being disposed in the supply pipes extending from a common ring pipe to the individual bulkhead compartments, the said non-return valves being actuated respectively in accordance with the pressure differential existing across them that they control the selection of the path for the replacement or drawing-off of gas so as to maintain practically the same pressure in all the chambers connected to a ring pipe.

The gas supply plant according to the invention is consequently so arranged that the refilling of the circuitbreaker high pressure chambers with the required switching gas is controlled by a solenoid valve which is centrally located, that is to say situated between a common high pressure reservoir and a high pressure ring pipe, and that a non-return valve contained in the corresponding supply pipe is provided for each circuitbreaker high pressure chamber and these non-return valves open in the direction of the respective circuitbreaker high pressure chamber when a determined pressure difference exists upstream and downstream of the valve, so that they effect the selection of the replenishment path into the individual circuit-breaker high pressure chamber or chambers. According to a further development of the invention, the central solenoid valve can be controlled by means of pressure monitors which are associated with the individual circuit-breaker high pressure chambers and which open the central solenoid valve when the pressure falls below the required switching pressure.

In order to achieve controlled drawing-off of the soiled extinguishing gas with simple means, according to a further development of the invention, pressure differential operated one-way valves are provided in the supply pipes leading from a common low pressure ring pipe, which is in communication with the suction side of a compressor, to the individual low pressure chambers, the said one-way valves opening in the direction of the ring pipe, while in addition, pressure monitors associated with each low-pressure chamber are provided in order to control the compressor, the extin-' guishing gas being drawn off from the low pressure chambers down to the same predetermined pressure through the control action of the correspondingly adjusted non-return valves.

For the purpose of making up any losses through leakage, as a further development of the invention, there may be provided in the gas supply plant an insulating pressure ring pipe which is connected to one or more reserve gas cylinders and from which branch pipes lead to the individual insulating bulkhead chambers, the release of the gas required being effected by a solenoid valve which is located centrally, that is to say between the gas cylinder and the ring pipe, and which is controlled in dependence on pressure, while in the aforesaid branch pipes leading to the individual insulating bulkhead chambers there may be provided one-way valves which open in the direction of the insulating bulkhead chambers in the event of a determined difference existing between the pressures upstream and downstream of the valve, so that they effect the selection of the replenishment path to the individual insulating bulkhead chamber or chambers.

The advantages which can be achieved through the invention consist above all in that a total of only two central solenoid valves are now required for the automatic control of the replenishment of the circuitbreaker high pressure chambers with compressed gas and for the replenishment of the insulating bulkhead chambers with insulating gas in order to make up any losses through leakage, even or switchgear consisting of a plurality of gas-blast circuit-breaker groups, while the replenishment path or the gas is selected by means of less expensive non-return valves.

A preferred embodiment of the invention is illustrated in the drawing and described more fully below. The single view of the drawing shows the schematically represented gas circuit plan of the gas supply plant according to the invention.

The illustrated embodiment comprises switchgear for the switching of three-phase lines; however, for the sake of simplicity, the installation is shown in the drawing as a singlepole arrangement. It consists of several gas-blast circuit-breaker groups of which two, namely the groups A, and A,,, are shown in the drawing.

The circuit-breaker high pressure chambers are designated l 1,, and the low pressure chambers 8, 8,,. Between the high pressure and low pressure chambers there is disposed, in each case, a switching section 29, -29 with an associated blast valve 7, 7,,, these valves allowing the gas to flow out of the high pressure chambers through the switching sections to the low pressure chambers when switching operations are carried out. For the purpose of supplying the circuit-breaker high pressure chambers l, l, a high pressure ring pipe 6 is provided which is connected to a common high pressure reservoir 2. Fromthe high pressure ring pipe 6 supply pipes 24, 24,, branch off to the individual circuit-breaker high pressure chambers. The circuitbreaker high pressure chambers are now automatically supplied with compressed gas from the high pressure reservoir 2, via the central solenoid valve 3 provided in accordance with the invention, as soon as one of the pressure monitors 4, 4 associated with the individual circuit-breaker high pressure chambers signals a drop in pressure below the necessary switching pressure and thereupon effects the opening of the central solenoid valve.

In addition, a one-way valve 5, 5,, located in the corresponding supply pipe 24, 24,, is associated with each circuit-breakerhigh pressure chamber. These one-way valves open in the direction of their respective circuitbreaker high pressure chamber when a determined difference in pressure exists upstream and downstream of the valve, so that they effect the selection of the replenishment path into the individual circuit-breaker high pressure chamber or chambers. At the same time the one-way valves 5, 5,, prevent the circuit-breaker high pressure chambers connected in parallel from emptying in the event of a defect occurring in one of them or in the high pressure ring pipe 6. As already stated, these one-way valves are so adjusted that they permit passage only in the event of a determined difference in pressure upstream and downstream of them existing. This difference in pressure naturally occurs first at the one-way valve at which the lowest pressure on the secondary side prevails. In order to ensure perfect functioning of this selection, the adjusted difference response pressure must simply be higher than the maximum pressure drop occurring in the ring pipe .6 between the one-way return valve 5,, located nearest to the inlet and that located farthest from the inlet.

The casing 28 of the switchgear contains the previously mentioned circuit-breaker high pressure chambers l, l,,, in which the power circuit-breakers 29, 29,, with movable contacts and fixed co-acting contacts are located, and also the low pressure chambers 8, 8,,. 30,- 30,, and 31,- 31,, designate isolating switches and 32, 32,, designate the power supply conductors, while 14, 14a, 14a,, and 14b, l4b,, designate the various insulating bulkhead chambers of the switchgear. 33, 33,, designate a connecting line between the insulating bulkhead chambers.

12 designates a common low pressure ring pipe, which is in communication, on the one hand, with the suction side of a compressor 10 and on the other hand, by way of supply pipes 25, 25,,, with the individual low pressure chambers 8, 8,,. Each of the supply pipes 25, 25,, contains a one-way valve 13, 13,,, these valves opening in the direction of the ring pipe 12. For the purpose of controlling the compressor 10, each low pressure chamber is provided with a pressure monitor 9, 9,,, the extinguishing gas being drawn off from .the low pressure chambers 8, 8,, to an equal predetermined pressure through the control action of the correspondingly adjusted non-return valves 13, 13,,.

On each disconnection operation, extinguishing gas flows out of the corresponding high pressure chambers l, 1,, through the blast valves 7, 7,, into the soiled" low pressure chambers 8, 8,,. The pressure monitor of the section whose low pressure exceeds a predetermined value puts into operation the compressor 10, which by way of the filter 11 reduces the low pressure to a likewise predetermined value. All the low pressure chambers 8, 8,, are thus lowered to practically the same pressure value if the flow resistance in the low pressure ring pipe 12 is low in relation to that of the individual one-way values 13, 13,,. The pressure side of the compressor 10 is in communication through a pipe 35, which contains a one-way valve 34, with the pipe I leading from the common high pressure reservoir 2 to the central solenoid valve 3. The one-way valve 34 prevents gas from returning from the high pressure part to the low pressure part.

In order to make up any losses which may occur through leakage, the circuit described above may be supplemented by one or more reserve gas cylinders 15 which are connected to an insulating pressure ring pipe 20. From this insulating pressure pipe, branch pipes lead to the individual insulating bulkhead chambers 14, 14a, 14a and 14b, l4b,,. A central solenoid valve 16 controlled in dependence on pressure is provided between the gas cylinder or cylinders 15 and the ring pipe 20. The pipes leading to the individual insulating bulkhead chambers contain one-way valves 18, 18a,

18a and 18b, l8b,,, which open in the direction of the insulating bulkhead partitions when a determined difference exists between the pressures upstream and downstream of the valve. Finally, for the purpose of operating the central solenoid valve 16 the individual insulating bulkhead chambers are provided with pressure monitors 17, 17a, 17a,, and 17b, l7b,,, which effect the opening of the solenoid valve 16 when the insulating pressure falls below a predetermined value. These one-way valves 18, 18a, 180,, and 18b, 18b,, also prevent the insulating bulkhead chambers 14, 14a, 14a,, and 14b, 14b,, connected in parallel from emptying in the event of a defect occurring in one of these chambers or in the insulating pressure ring pipe 20.

The pressure monitors 9, 9,, associated with the low pressure chambers 8, 8,, may also be so constructed that, in addition to their previously described function of controlling the compressor 10, they also act on the solenoid valve 16 so' as to open it when the gas pressure in one of the low pressure chambers 8, 8,, falls below a predetermined value. In order to make up any leakage losses in any of the low pressure chambers, these chambers are connected in parallel to the insulating bulkhead chambers 14, 14a, 14a,, and 14b, 14b,, via pipes 26,- 26,, containing one-way valves 19, 19,,, and are connected to the leakage loss supply and to the insulating pressure ring pipe 20. The arrangement is such that the pipes containing the one-way valves 19 19,, are connected to the corresponding pipes 25, 25,, in each case at a point 27, 27,, which lies between the appertaining low pressure chamber 8, 8,, and the corresponding one-way valve 13, 13,,. v Leakage losses are now made up in the following manner: when the pressure in one of the insulating bulkhead chambers 14, 14a, 14a,, and 14b, l4b,,, or

replenishment path is then effected by the one-way' valves 18, 18a, 18a,,, 18b, 18b,, and 19, 19,, via the ring pipe 20 in accordance with the same principle as in the case of high pressure replenishment. In addition, the one-way valves 19, 19,, have the function of preventing any overflow of soiled extinguishing gas into the insulating bulkhead chambers.

Leakage losses from the circuit-breaker high pressure chambers 1, 1,,, and also from the high pressure reservoir 2, can be made up from another gas cylinder 21, which is connected by a pipe 36 to the reservoir 2. For this purpose, the pressure monitor 22 of the reservoir 2 puts into operation a solenoid valve 23, which is located in the pipe 36, when the pressure in the reser-' voir falls below the required value, thus enabling compressed gas to low from the compressed gas cylinder 21 to the reservoir 2 or in the direction of the ring pipe 6..

high pressure chambers and including branch pipes leading respectively therefrom to each of said high pressure chambers, each said high pressure branch pipe including a one-way valve openable automatically in the direction towards said high pressure chamber in response to a determined pressure differential across the one-way valve, a low pressure gas return pipe common to all gf said low lressure chambers and including branch pipes leading respectively thereto from each of said low pressure chambers, each said low pressure branch pipe including a one-way valve openable automatically in the direction away from the low pressure chamber in response to a determined pressure differential across the one-way valve, a compressor having its inlet side connected to said common low pressure gas return pipe for withdrawing contaminated gas from said low pressure chambers and having its outlet side connected through a control valve to said common high pressure gas supply pipe and to a high pressure gas reservoir, high pressure monitoring means provided respectively for each of said high pressure chambers for separately controlling the operation of said control valve in response to a determined drop in pressure, and low pressure monitoring means provided respectively for each of said low pressure chambers for separately controlling the operation of said compressor.

2. A switchgear plant as defined in claim 1 wherein each of said switchgear sections includes gaspressurized insulating bulkhead chambers located respectively adjacent to the high and low pressure chambers of the switchgear section and which include an isolating switch connected in series with the contacts of the switching section, a pressurized gas supply pipe common to all of said insulating bulkhead chambers and including branch pipes leading respectively therefrom to each of said insulating bulkhead chambers, each of said branch pipes including a one-way valve openable automatically in the direction towards said insulating bulkhead chamber in response to a determined pressure differential across the valve, a reserve gas cylinder connected through a control valve to said common pressurized gas supply line, and pressure monitoring means provided respectively for each of said insulating bulkhead chambers for separately controlling the operation of said control valve when the respective pressure falls below a predetermined insulating pressure.

3. A switchgear plant as defined in claim 2 wherein the low pressure gas return branch pipe from the low pressure chamber of each switchgear section is connected to the branch pipe leading from the pressurized gas supply pipe to the insulating bulkhead chambers of each swithgear section by a pipe which includes a oneway valve openable in the direction towards said low pressure gas return branch pipe in response to a determined pressure differential across the one-way valve.

4. A switchgear plant as defined in claim 3 wherein the connection of said pipe including the one-way valve to the low pressure gas return branch pipe is made at a point in the latter intermediate said low pressure chamber and the one-way valve therein leading to said common low pressure gas return pipe.

5. A switchgear plan as defined in claim 3 wherein said low pressure monitoring means provided respectively for each of said low pressure chambers for controlling the operation of said compressor also control operation of the control valve connecting said reserve gas cylinder to said common pressurized gas supply line such that said control valve opens when the pressure in any one of said low pressure chambers falls below a predetermined insulating pressure.

' UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3: 9, Dated November 9, 97

Inventor(s) KARL HEINZ WAGNER, e'b 8.1,

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 2, line 1 L before "valve" insert:

- one way 5 Claim 3, line 6 spell "switcl'lgealr" thus [73] Assignee: BBC BROWN BOVERI 8c COMPANY LIMITED Baden, Switzerland Signed and sealed this 11th day of February 1975.

(SEAL) Attest:

C. MARSHALL DANN Commissioner of Patents and Trademarks RUTH C. MASON Arresting Officer UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3: 9, Dated November 9, 9W

Inventof s) et 8.1,

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown belowzf Clairh 2, line 1 L before "valve" insert:

-,ohe way 7 Claim 3, line 6 spell "switchgear" thus [73] Assignee: BBC. BROWN BOVERI 86 COMPANY LIMITED Baden, Switzerland Signed and sealed this 11th day of February 1975.

(SEAL) Attest:

c. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks 

1. A switchgear plant comprising a plurality of gas-pressurized switchgear sections each of which includes a high pressure chamber containing therein a contact switching section and a low pressure chamber connected to said high pressure chamber by means of a blast valve actuatable to open position upon disengagement of the contacts of the switching section thereby to effect a discharge of arc-contaminated gas from the high pressure chamber into the low pressure chamber, a high pressure gas supply pipe common to all of said high pressure chambers and including branch pipes leading respectively therefrom to each of said high pressure chambers, each said high pressure branch pipe including a one-way valve openable automatically in the direction towards said high pressure chamber in response to a determined pressure differential across the one-way valve, a low pressure gas return pipe common to ll of said low pressure chambers and including branch pipes leading respectively thereto from each of said low pressure chambers, each said low pressure branch pipe including a one-way valve openable automatically in the direction away from the low pressure chamber in response to a determined pressure differential across the one-way valve, a compressor having its inlet side connected to said common low pressure gas return pipe for withdrawing contaminated gas from said low pressure chambers and having its outlet side connected through a control valve to said common high pressure gas supply pipe and to a high pressure gas reservoir, high pressure monitoring means provided respectively for each of said high pressure chambers for separately controlling the operation of said control valve in response to a determined drop in pressure, and low pressure monitoring means provided respectively for each of said low pressure chambers for separately controlling the operation of said compressor.
 2. A switchgear plant as defined in claim 1 wherein each of said switchgear sections includes gas-pressurized insulating bulkhead chambers located respectively adjacent to the high and low pressure chambers of the switchgear section and which include an isolating switch connected in series with the contacts of the switching section, a pressurized gas supply pipe common to all of said insulating bulkhead chambers and including branch pipes leading respectively therefrom to each of said insulating bulkhead chambers, each of said branch pipes including a one-way valve openable automatically in the direction towards said insulating bulkhead chamber in response to a determined pressure differential across the valve, a reserve gas cylinder connected through a control valve to said common pressurized gas supply line, and pressure monitoring means provided respectively for each of said insulating bulkhead chambers for separately controlling the operation of said control valve when the respective pressure falls below a predetermined insulating pressure.
 3. A switchgear plant as defined in claim 2 wherein the low pressure gas return branch pipe from the low pressure chamber of each switchgear section is connected to the branch pipe leading from the pressurized gas supply pipe to the insulating bulkhead chambers of each swithgear section by a pipe which includes a one-way valve openable in the direction towards said low pressure gas return branch pipe in response to a determined pressure differential across the one-way valve.
 4. A switchgear plant as defined in claim 3 wherein the connection of said pipe including the one-way valve to the low pressure gas return branch pipe is made at a point in the latter intermediate said low prEssure chamber and the one-way valve therein leading to said common low pressure gas return pipe.
 5. A switchgear plan as defined in claim 3 wherein said low pressure monitoring means provided respectively for each of said low pressure chambers for controlling the operation of said compressor also control operation of the control valve connecting said reserve gas cylinder to said common pressurized gas supply line such that said control valve opens when the pressure in any one of said low pressure chambers falls below a predetermined insulating pressure. 